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What does Varifocal mean?

If a camera is equipped with a vari-focal lens, that means its focal length can be adjusted anywhere between its designated range.

The Focal Length determines the field of vision.

The smaller the focal length, the wider the field of vision.

Take a look at the images below. Look how the church seems to zoom in as the size of the lens is changed.

The camera is the same distance from the church in each photo. A person can zoom in on the subject. Notice the sides of the street show less the more the camera zooms.

The principle is to adjust for the greatest amount of zoom effect, and therefore the most detail, and still cover the width of the field of vision desired.

Below, the photos shows the actual width of the field of vision at different lens settings but at the same distance.

It is important that you choose a camera with varifocal lens technology if you are new to the technology and want to have your first project a success.

CCTV Lens Comparison Chart

CCTV lens

 

Focal Length
Angle
 
2.5mm
120°
https://cctvgold.com/assets/images/General/Lenscompare/2-5.gif
3.6mm
92°
https://cctvgold.com/assets/images/General/Lenscompare/3-6.gif
4.3mm
78°
https://cctvgold.com/assets/images/General/Lenscompare/4-3.gif
6.0mm
53°
https://cctvgold.com/assets/images/General/Lenscompare/6-0.gif
12mm
25°
https://cctvgold.com/assets/images/General/Lenscompare/12.gif
25mm
18°
https://cctvgold.com/assets/images/General/Lenscompare/25.gif

https://cctvgold.com/assets/images/General/Lenscompare/5-100.jpg

Competitor's Website - Excellent Examples of Field of View Comparisons - Click Here

lens
size
Field of View (in ft.)
5 ft
away
10 ft
away
15 ft
away
25 ft
away
50 ft
away
100 ft
away

mm

w
h
w
h
w
h
w
h
w
h
w
h
3.6 7.5 5.2 15.1 10.4 22.6 15.6 37.7 26.1 75.4 52.1 151 104
6.0 3.8 2.9 7.7 5.7 11.5 8.6 19.2 14.4 38.4 28.7 77 57
8.0 2.9 2.1 5.7 4.3 8.6 6.4 14.4 10.7 28.7 21.3 57 43
12.0 1.9 1.5 3.9 3.0 5.8 4.5 9.7 7.5 19.4 14.9 39 30

Lens Calculator - Try It!!

https://cctvgold.com/assets/images/General/Lenscompare/FOV.gif

Competitor's Website - Excellent Examples of Field of View Comparisons - Click Here

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